The present invention relates to a method for the generation of a nearly monodispersed aerosol in filter-testing penetrometer machines.
The present invention is superior to the previous process in that it employs a candidate mixture as a replacement for dioctyl phthalate (DOP), which is a suspected carcinogen. In the following discussion, the term "Candidate Material" will be used to designate an aerosol mixture made up of the following: poly alpha olefin having chain lengths in percentages of about, by volume, of 30.9% of 30 carbon atoms, 42.8% of 40 carbon atoms, 20.4% of 50 carbon atoms, 4.8% of 60 carbon atoms, and 1.1% of 70 carbon atoms. The term poly alpha olefin in this case is called also a synthetic hydrocarbon 6 CST fluid. The CST refers to centistokes, a measure of viscosity. The number ahead of CST fluid specifies the viscosity at 100 degrees C. The candidate mixture is manufactured by Henkel Corporation, Emery Group, 11501 Northlake Drive, P.O. Box 429557, Cincinnati, OH 45249. The candidate mixture has been identified by us as a thermally stable material of low toxicity.
For several decades, the U.S. Army has produced hot smokes using DOP as the standard material in the performance of nondestructive gas mask and filter serviceability testing. Hot smokes are aerosols produced using a method of thermally-generated vaporization and recondensation (self nucleation) of particles. Heated air passes across the surface of a heated liquid (DOP); cooler air then merges with the vapor causing recondensation of an aerosol or "hot smoke." The U.S. Army Surgeon General has designated DOP as a suspected carcinogen and has prohibited or severely restricted its use in smoke-generating machines used to test U.S. Army masks, respirators, filters, and other personnel protection equipment.
The ATI model TDA-100 (Q-127) monodispersed filter penetrometer is manufactured by Air Techniques, Inc. (ATI), a Division of Hamilton Associates, Inc., 1716 Whitehead Road, Baltimore, MD 21207. A description of this equipment is given elsewhere in this disclosure. Thus, the candidate material and process have been shown to be acceptable to the manufacturer for specification in his new machines.